I am trying to figure out why my computer doesn't wake up properly from sleep, which happens about 3 times out of 5 (see update below). Fans and HDDs spins up and looks to be working (according to LED), but my monitor doesn't get any signal from the GFX-card so I am forced to do the infamous norwegian (hard) reboot.

At first I thought it was a faulty HDD (old 2nd gen WD Raptor) that was causing these issues since I got spammed with warning messages about drive inaccessibility from Intel Rapid Storage Technology evertime this happened.

Since I was getting data corruption as well I decided to superannuate my faithful Raptors and replace them with brand new SSDs. At the same time I reinstalled Windows 7, to no avail. The problem persists!

I am using the latest BIOS, firmwares and drivers for all the hardware, so I do not believe this to be software-related and since I now can deduct the faulty HDD from the equation I suspect it might be the PSU that has a hard time feeding the current for the GFX-card card when waking up from sleep.

So I'm all out of ideas, which is why I'm asking you SUs for help. Any thoughts?

UPDATE: I've done some extensive testing based on the current answers and it seems that this only happens when the computer has been in sleep for a longer period of time (over an hour). I've made sure there's no hybrid sleep going on (hybernation is toggled off anyways), so that can't be the case. To me everything points to the PSU not being able to provide the necessary currents at a "cold start". Could this be the case?

UPDATE 2: Bought a new PSU which seems to have resolved the problem. See my own answer below for more details.

UPDATE 3: Problem is now resolved. See accepted answer for more details.

If the power supply couldn't start it up, it would fail to cold boot. It's more likely that the power supply is not reliable at low draws, and eventually fails to supply enough power to keep the RAM alive.
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CarlFOct 11 '11 at 12:38

Bought myself a new PSU (Corsair AX750) and the problem seems to have resolved itself. Left the computer sleeping during the night and woke it up without any issues this morning. I will have to do some more testing to confirm it and will update both this answer and my question when I got the results.

UPDATE: After some extensive testing I can confirm this problem to be solved. I haven't once run into trouble waking it up from sleep. However, I occasionally get BSODs instead but this is most likely due to the SSDs and the drivers and not related to this problem.

Huh! That's a weird problem, given that you had plenty of PSU capacity I didn't even think to suggest it. Maybe it wasn't performing up to spec...it's certainly not out of the question for it to have caused problems.
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ShinraiOct 14 '11 at 14:14

@Shinrai, it was only happening when I was cold-booting. So I guess it might be the capacitors that didn't cope with the high load at boot. There were other signs pointing to this as well, such as the leds fading in/out and the fans mysteriously changing RPM, like a voltage rollercoaster :)
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Marcus EkwallOct 14 '11 at 14:51

Oh, geez, I never noticed your update about the cold boot thing. That and the other stuff you just mentioned has me totally on board now - VERY plausible.
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ShinraiOct 14 '11 at 15:10

I did this several times, but I can't find anything of interest in the logs. It recommends me to change my settings to be more "energy efficient", but there's no info to indicate any real problem.
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Marcus EkwallOct 11 '11 at 7:54

It shouldn't really change significantly between runs. If there's a device driver that it causing significant problems going into and out of sleep mode, it should flag that, so the fact that it didn't is significant - that, combined with the fact that you have only sporadic trouble, tells me it's probably a software service (one that's not always running, or is always running but isn't always doing the same thing) that's the culprit. I'd disable anything that runs in the background that I could and see if it clears up your issues.
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ShinraiOct 11 '11 at 15:02

FWIW, I personally don't recommend EVER sleeping a desktop PC for exactly this reason - these problems are not uncommon.
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ShinraiOct 11 '11 at 15:03

My desktop is utterly reliable returning from suspend ("sleep") but fails about 5% of the time returning from hibernation. Single data point.
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CarlFOct 13 '11 at 17:52

@Shinrai, sleeping have never been an issue for me. Sure, only takes 10 seconds to boot but I like session persistency and do not want to have my computer on at all times.
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Marcus EkwallOct 14 '11 at 6:57